Saturday, September 25, 2010

Decadal Survey Endgame

A single presentation slide has been posted on the planetary Decadal Survey webpage listing the schedule towards the public release of the recommendations (next spring) and final document (next August).  (Slide reproduced below.)  The draft report and recommendations should now be with reviewers.  The Surveys traditionally have run a tight review process with no leaks, so the public will have to wait six months to learn what the next decade's program will look like (assuming budgets come through and no major cost overruns).

However, it's fun to speculate what the recommendations might look like.  With that in mind, I'll publish my best guess on what the Survey might recommend.

The last planetary Decadal Survey had four themes to guide mission selection.  I have not seen anything that I predict will replace these priorities althought they are likely to be updated: 1. The First Billion Years of Solar System History; 2. Volatiles and Organics: The Stuff of Life; 3. The Origin and Evolution of Habitable Worlds; 4. Processes: How Planetary Systems Work.

Two key missions from the last Survey have yet to receive formal approval: an Europa orbiter and Mars sample return.  Both remain highly relevant to the priorities listed above.  Both I think are likely to be recommended in the next Survey.  (Both are also expensive, so this is the prediction that I have the least confidence in.)  Titan and Enceladus have increased in importance, but technology is not yet ripe for a multi-billion dollar Flagship mission to these targets.  I predict that the Survey will recommend a lower cost missions to these moons as a gap filler in the next decade.  Scientist-led Discovery and New Frontiers missions also are likely to remain a priority to balance out the program with missions to additonal targets.

Based on these assumptions (and some will be proved wrong), here is a program that would address them and that would fit within the current budget adjusted for inflation over a full decade (costs are either based on publically published numbers or are swags (MTGO and Titan/Enceladus):

Some notes on this possible program:

The Mars missions would provide a head start on a Mars sample return.  However, I would not start the subsequent elements of the return until a cache is ready on the surface of Mars with samples known to be high priority

If budgets prove tight, I would cut the Jupiter Europa Orbiter back to ~$2B to focus only on the most urgent measurements (and sacrifice a good portion of the Jupiter system science).  A Discovery mission might also be cut.

In this thought experiment, the Titan/Enceladus mission would a PI-led mission that would substitute for a second New Frontiers mission in the decade.  The suggested budget would cover the cost of a New Frontiers-class orbiter and a Discovery-class in-situ element such as a lake lander or a plane.  What might be actually proposed by the winning PI might be quite different.

The 2011 New Frontiers mission would be selected from the three missions currently in competition: a Venus lander, a near Earth asteroid sample return, or a lunar sample return.

I have been impressed with the creativity of the Discovery mission proposals and suggest four missions in the coming decade.  Now that NASA no longer requires the launcher to be paid out of the PI budget, capable missions should be able to be flown.  The PI for the proposed Io Volcano Observer, for example, has said that the previous budget limits didn't quite work, but that the new budget limits would fully fund this mission.  (The budget suggested, though, is based on NASA's full cost, which includes launchers and other items.)

There are many losers in terms of exciting and important missions that wouldn't be included in this guess at what the Survey might recommend.  The two that I personally would most regret not seeing would be the proposed Argo Neptune-Triton-KBO mission and a Mars network mission.

When the Survey publishes its recommendations, I'll come back and score my predictions.  I hope I do better here than I have done picking stocks :>

Thursday, September 16, 2010

Exploring the Interior of a Comet

Note: While I'm traveling this month with only occasional short access to the internet, I'm reading through some of the back log of proposed mission concepts.  I'll post short summaries of the more interesting ideas.  Unfortunately, I'm unlikely to have time to search down internet sites to provide hot links to the abstracts and presentations I'm reading.  I'll try to provide sufficient information on each that you hopefully can easily do a search to find the original documents.

In this post, I'll a mission concept for the Discovery program (~$425M PI cost, ~$800M fully burdened cost) that would explore the interior of a comet.

The proposal was described in an extended abstract (2 pages) for this year's 41st Lunar and Planetary Science Conference.

Deep Interior Radar Imaging of Comets
LPSC abstract 2670.pdf

One surprise of our exploration of asteroids and the tiny moons of Mars is that many small bodies appear to be rubble piles loosely held together by gravity.  We know little about the interior of comets (fast, distant flybys produce poor gravity measurements).  However, as the authors of the abstract state, the early reconnaissance of comets "has so far yielded the discovery of an unanticipated range of diversity in geomorphic forms: multiplicities of pits, craters with vertical overhangs, global scale layering, mesas and plains.  It has also revealed new geological processes that are revolutionizing our concepts of the cometary interior -- the discovery of repetitive mini-outburts, of patches of enhanced H2O ice, and of caldera-like depressions and smooth flows... It is time to capitalize on these discoveries by moving into a new, detailed exploratory phase where we learn how comets work."

The authors propose to use ice penetrating radar to produce images of the interior of a comet with 10 m resolution that would be comparable to a "medical ultrasonographic brightness scan."  Ice and ground penetrating radars have a long heritage both from airplanes for Earth studies and at Mars where they have successfully explored the upper few kilometers of the Martian crust.  For a small comet -- the proposed target is the 3 km diameter 79P/duToit-Hartley comet -- the radar could study the entire interior as the spacecraft orbits the spinning comet.

The authors note that the Rosetta mission will conduct an inital probe of the interior of a comet as it tracks radio waves from its Philae lander through the body of a comet.  They imply that radar would offer superior interior imaging, but acknowledge the contribution the Rosetta mission will make.

The authors do not state whether or not they have proposed this mission for the current Discovery mission selection.

Editorial thoughts: I don't know if the radar system required for this mission is so costly that a dedicated mission would be needed.  Ice penetrating radars come in different flavors.  The radar proposed for NASA's Jupiter Europa Mission, for example, is a more capable and massive (and mass tends to be strongly correlated with instrument cost) than the radar proposed for ESA's Jupiter Ganymede Mission.  It would seem to me that a spacecraft capable of additional studies such as surface imaging and compositional studies of emitted gases and dust in addition to the radar instrument would be a very attractive mission.  However, the radar unit may be too costly for a Discovery-class mission to fly additional instruments.  The abstract does not provide any information on this.

I have also been struck by the diversity of comet surfaces we have seen from the few flyby spacecraft to date.  Their interiors may be equally varied.  It may be that rather than one mission providing a definitive answer, ice penetrating radar may be needed on a number of comet missions before we begin to understand that variety and the processes that created it.

Solar Probe Plus

Note: While I'm traveling this month with only occassional short access to the internet, I'll post the full text of interesting press releases rather than abstract them and provide additional background as I normally do.
September 02, 2010

PASADENA, Calif. -- NASA has begun development of a mission to visit and study the sun closer than ever before. The unprecedented project, named Solar Probe Plus, is slated to launch no later than 2018.
The small car-sized spacecraft will plunge directly into the sun's atmosphere approximately 6.4 million kilometers (four million miles) from our star's surface. It will explore a region no other spacecraft ever has encountered. NASA has selected five science investigations that will unlock the sun's biggest mysteries, including one led by a scientist from NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"The experiments selected for Solar Probe Plus are specifically designed to solve two key questions of solar physics -- why is the sun's outer atmosphere so much hotter than the sun's visible surface and what propels the solar wind that affects Earth and our solar system? " said Dick Fisher, director of NASA's Heliophysics Division in Washington. "We've been struggling with these questions for decades and this mission should finally provide those answers."
As the spacecraft approaches the sun, its revolutionary carbon-composite heat shield must withstand temperatures exceeding about 1,400 degrees Celsius (2,550 degrees Fahrenheit) and blasts of intense radiation. The spacecraft will have an up-close and personal view of the sun, enabling scientists to better understand, characterize and forecast the radiation environment for future space explorers.
NASA invited researchers in 2009 to submit science proposals. Thirteen were reviewed by a panel of NASA and outside scientists. The total dollar amount for the five selected investigations is approximately $180 million for preliminary analysis, design, development and tests.
The selected proposals are:
-- Solar Wind Electrons Alphas and Protons Investigation: principal investigator, Justin C. Kasper, Smithsonian Astrophysical Observatory in Cambridge, Mass.
This investigation will specifically count the most abundant particles in the solar wind -- electrons, protons and helium ions -- and measure their properties. The investigation also is designed to catch some of the particles in a special cup for direct analysis.
-- Wide-field Imager: principal investigator, Russell Howard, Naval Research Laboratory in Washington. This telescope will make 3-D images of the sun's corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft, providing direct measurements by imaging the plasma the other instruments sample.
-- Fields Experiment: principal investigator, Stuart Bale, University of California Space Sciences Laboratory in Berkeley, Calif. This investigation will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the sun's atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft's antenna.
-- Integrated Science Investigation of the Sun: principal investigator, David McComas of the Southwest Research Institute in San Antonio. This investigation consists of two instruments that will take an inventory of elements in the sun's atmosphere using a mass spectrometer to weigh and sort ions in the vicinity of the spacecraft.
-- Heliospheric Origins with Solar Probe Plus: principal investigator, Marco Velli of JPL. Velli is the mission's observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.
"This project allows humanity's ingenuity to go where no spacecraft has ever gone before," said Lika Guhathakurta, Solar Probe Plus program scientist at NASA Headquarters, in Washington. "For the very first time, we'll be able to touch, taste and smell our sun."
The Solar Probe Plus mission is part of NASA's Living with a Star Program. The program is designed to understand aspects of the sun and Earth's space environment that affect life and society. The program is managed by NASA'S Goddard Space Flight Center in Greenbelt, Md., with oversight from NASA's Science Mission Directorate's Heliophysics Division. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., is the prime contractor for the spacecraft.
For more information about the Solar Probe Plus mission, visit:

Tuesday, September 7, 2010

Lunette: Reducing Network Mission Costs

Note: While I'm traveling this month with only occasional short access to the Internet, I'm reading through some of the back log of proposed mission concepts.  I'll post short summaries of the more interesting ideas.  Unfortunately, I'm unlikely to have time to search down Internet sites to provide hot links to the abstracts and presentations I'm reading.  I'll try to provide sufficient information on each that you can easily do a search to find the original documents.

In this post, I'll a mission concept for the Discovery program (~$425M PI cost, ~$800M fully burdened cost) that would explore the moon's interior.

The proposal was described in an extended abstract (2 pages) for this year's 41st Lunar and Planetary Science Conference.

Lunnette: Establishing a lunar geophysical network without nuclear power through a Discovery-class mission
LPSC abstract 2710.pdf

Studies of the interiors of the moon and planets has been repeatedly prioritized by review panels prioritizing future planetary exploration.  Planets and large moons have had complex interactions between the formation, evolution, and current state of their interiors and surfaces and, where they exist, their atmospheres.  While surfaces and interiors have received considerable attention, interiors have received much less investigation.  Gravity measurements from orbiters and flybys provide some information on interiors, but seismic and heatflow measurements are considered essential to extend our knowledge.  To date, only the moon has been investigated by a network of surface stations left by the Apollo astronauts.  Those instruments represent decade old technologies and were placed at sites chosen for surface geology rather than optimizing the design of the network.

The Lunette proposal attempts to address one of the major roadblocks to establishing surface networks, cost.  The current leading proposal for an initial four node lunar network, the International Lunar Network (ILN), reportedly would cost more than a New Frontiers mission (~$650M PI cost, ~$1.2B fully burdened cost).  I've seen estimates for a four node Mars network in the range of $1.5B.

The Lunette proposal would minimize costs through three strategies.  First it would use solar power in place of nuclear power and would "use new power management technology" to survive and operate through the long lunar night for at least two years of operation.  Second, it would place just three nodes on the surface instead of ILN's four.  And third, it would depend on international partners to supply and pay for a very broad band seismometer that would be an order of magnitude more sensitive than the Apollo seismometers, a short period seismometer, and a heat flow probe.  U.S. scientists would supply a low-frequency electromagenetic sounding instrument and a laser retroreflector.

Editorial thoughts:  Studying planetary interiors is important.  Two NASA missions in development, the JUNO Jupiter orbiter and the GRAIL lunar orbiters would study the interiors of their bodies using gravity and magnetometer measurements.  Studying the interiors of the moon and Mars from the surface is the next logical step.  If the Lunette team has found ways to dramatically reduce costs for surface networks, that would be welcome news.  The list of authors includes two authors from JPL, suggesting that the engineering analysis may be reasonably advanced.  (I don't recognize these author's names and so don't know if they are on the science or engineering side of JPL, and I can't do a web search from the tent I'm writing this in.)  On the other hand, the costs of many Discovery proposals reportedly have proven to have under estimated costs in the eyes of the panels that review the proposals.  Getting a network mission into even the cost cap of a New Frontiers mission would still be a significant achievement, though.  The Lunette proposal sounds like solid progress in that direction.